Eye tracking: what is it, what types it is and what is it for

It is said that the eyes are the window to the soul, but they also allow us to know how we look at the details of a painting, the parts of our body that we look at the most when we are in front of the mirror or the that catches our attention in an ad.

Eye tracking, or eye tracking, is a process in which eye movement is measuredSo you can determine where, what and for how long a person is watching.

The eyes are perhaps the most important organs through which we obtain information from the world, which is why eye-tracking techniques have become increasingly important in research. Let’s take a closer look at these techniques.

    What is eye tracking?

    Eye tracking, also known as eye tracking, refers to the set of techniques that allow you to assess where a person is looking, what particular object or detail you focus on and how long you keep your gaze fixed. Devices that perform this technique are called “eye trackers” and consist of several different types of devices that allow you to watch the angle of view or the movement of the eye itself.

    Eye tracking techniques have been used in research in different fields, such as cognitive linguistics, psychology as well as marketing and product design.. These are techniques that allow us to know the visual behavior of a person, whether it is a subject, a patient or a buyer, and based on this, draw conclusions about their interests, their emotional state or even if they have any pathology.

    the story

    Although eye-tracking techniques today use modern devices that record eye movement or direction of gaze, the truth is that the earliest attempts to find out where people were looking when performing some type of task can be traced back to in the 19th century. These early attempts were made by direct observation of where the subject was looking, and what type of information or striking stimulus had been presented to him in his field of vision.

    Louis Emile Javal, in 1879, it was observed that, when reading, the reading process did not involve a light sweep of the eyes throughout the text. Until then, it was believed that when reading, say, a book, each line was followed from start to finish, without skipping or being “stuck” for a few seconds in a single word. Javal observed that the reading was, in fact, a series of short stops, stares and quick jerking movements.

    During the 20th century, attempts were made to resolve various questions about reading, such as which words were interrupted the most, how much time was spent on them, or how and why they came back and reread words that were already been read. Edmund Huey, with the intention of solving these questions, designed a contact lens with a hole placed directly in the participant’s eyes. With these lenses, I was able to record, very precisely, the movement of the eyes when I read and what I watched.

    since Huey’s technique was, while objective and effective, quite boring and invasive.Other researchers invented their own “eye trackers,” which limited themselves to accurately recording eye movements without having to insert anything into the participant’s eye. One of them, Guy Thomas Buswell, was the one who designed the first non-invasive eye-tracking device, using light beams reflected back into the eye, and when the eyeball moved, the light beam was deflected, recording the process in a movie. .

    During the 1950s and 1960s it was discovered that eye movement, both in front of a text and an image, could be conditioned by the task to be performed by the participant or his interests. This was the case with the research of Alfred L. Yarbus, who came to the conclusion that eye movement did not only depend on what he had in front of the subject, but also influenced what he hoped to find.

    Today eye tracking devices have improved and become much more precise and less invasive. They have adapted not only to know the visual behavior of people in front of an image, a page of text or a face, knowing what people are looking at more. Since the 2000s eye monitoring devices have been manufactured for people with motor disabilities, Who interpret eye movements as commands, for example causing the wheelchair to move or to utter a sentence when looking at the words on a screen.

    Types of eye tracking

    Although most eye trackers today are non-invasive and use video recording, they are not the only and, strictly speaking, the most accurate. Below, we’ll take a look at the three main types of eye tracking.

    1. Invasive sensation

    It uses something that is attached to the eye, such as a contact lens with a built-in mirror. This type of eye tracking is quite invasive, as the name suggests, as it involves placing something in the subject’s eye that moves according to the movement of the eyeball.

    Since the eyes are delicate organs and people are usually very sensitive to touch, it often happens that the participant rejects the placement of an invasive sensitive eye tracker. It’s a pretty boring technique.

    But despite being annoying, eye trackers of this type have the advantage of allowing you to record eye movement quite accurately, as they move depending on how it is doing. The records obtained through this system are very detailed.

    2. Non-invasive feeling

    This tracking is done without the need for direct eye contact. Through light, such as infrared, eye movement is known by the reflection of the light beam, which is captured by a video camera or optical sensor.

    Non-invasive sensory eye trackers they usually use the corneal reflex and the center of the pupil to know the movement of the eyeball. Others also use the front of the cornea and the back of the lens. There are also those who engrave the inside of the eye, paying attention to the position of the blood vessels in the retina.

    In general, optical methods are well taken into account in the field of research, because their cost is low and they are not invasive.

    However, they may not register eye movements because sometimes they don’t accurately detect the pupil, cornea, or any eye mark they are using do eye tracking. In addition, if the subject closes their eyes, their visual behavior cannot be recorded.

    Some virtual reality devices, such as FOVE glasses, have eye trackers of this type, letting you know which places the person is looking at while immersed in the virtual environment.

    3. Electrical potentials

    A rather special eye-tracking technique is one that uses electrical potentials, measured with electrodes placed around the eyes.

    The eyes are the source of an electric potential field, which can be measured even with closed eyes.. The electrodes can be placed to generate a dipole, a positive pole in the cornea and a negative pole in the retina.

    The electrical signal obtained from this technique is called an electrooculogram (EOG). If the eyes move from the center to the periphery, the retina approaches one of the electrodes, while the cornea approaches the opposite.

    The main advantage of eye tracking using electrical potentials is that it is able to register eye movement even with closed eyelids, Since the magnetic field of the eye is recorded.

    However, its main drawback is that while it is not completely invasive, it does involve placing electrodes, which means scratching the subject’s skin a bit. In addition, the care of these electrodes is quite delicate, and they can fail very easily or not conduct current well depending on the subject’s skin.

    Eye tracking applications

    Eye tracking has been very useful in several areas, both theoretical and practical.

    Marketing and Website Design

    In marketing, eye tracking is a useful technique since it allows to know the visual patterns of buyersKnowing which details in an advertisement, whether on television, in newspapers or on the web, are more fixed.

    Thanks to this, companies can carry out quantitative studies on how communication, i.e. advertising, is perceived in the population and how to improve it. too much it is possible to know the impact of audiovisual advertising, both in a neutral context, that is to say experimental, and in life itself.

    By knowing which details users pay the most attention, it is possible to improve business websites to make them more eye-catching and manageable for potential buyers, as well as to keep their attention and direct them to the market. purchase of the product or service. .

    But not only eye tracking focus on how to promote products, But also in the way they should get carried away. With eye tracking, you can see which stimuli of a certain color, shape, or various visual characteristics the subject pays the most attention. In this way, companies can design their products and packaging to incentivize their purchase.

      People with Disabilities

      Eye monitoring has the great advantage of being able to help people with reduced mobility, such as people with quadriplegia or cerebral palsy.

      Eye tracking using non-invasive detection can be combined with computer monitors, In which letters appear that the user can look. Looking at these letters, a device forms words and phrases that resonate through a speaker, allowing people with speech difficulties to communicate.

      too much the same can be done to move the wheelchair. The person looks at the screen, which shows arrows indicating the direction. Looking at each of these arrows, send the order for the mechanized wheelchair to move in the desired direction.

      psychology

      By studying visual behavior, it is possible to know if a person exhibits some kind of pathology, or how their way of seeing things differs from what is expected in a person without a psychopathological diagnosis.

      It has been observed that people with attention deficit hyperactivity disorder decentralize their gaze much more easily than people without a diagnosis.

      This means they don’t pay enough attention to things like the chalkboard or textbook, encouraging learning and comprehension problems that can be mistaken, in the most severe cases, for dyslexia or even mental retardation. .

      It should be noted that eye tracking techniques can be very useful in diagnosing both ADHD and dyslexia because, although both have reading problems, the visual behavior pattern differs, the former being more decentralized. in the text, but ineffective.

      Eye tracking has also been used to observe and analyze the visual behavior of people with neurodegenerative diseases, Such as Alzheimer’s or Parkinson’s disease, and mental disorders such as schizophrenia, autism spectrum disorders, depression or brain damage.

      Special mention is its usefulness in eating disorders. With these devices, whether or not combined with virtual reality, you can find out what people with anorexia nervosa look like the most. Hopefully, they focus their gaze in particular on the places where they feel the most complex.

      Bibliographical references:

      • Adler FH and Fliegelman (1934). Influence of fixation on visual acuity. Bow. Ophthalmology 12, 475.
      • Buswell, GT (1922). Fundamental Reading Habits: A Study of Their Development. Chicago, IL: University of Chicago Press.
      • Fuster, Roger HS (1988); Eye movements (2nd ed.). Pion Ltd, London. ISBN 0-85086-109-8.
      • Huey, EB (1968). The psychology and pedagogy of reading. Cambridge, MA: MIT Press.
      • Yarbus, AL (1967). Eye movements and vision. Full up. New York.
      • Porras Garcia, Bruno & Ferrer-García, Marta & Ghiţă, Alexandra & Moreno, Manuel & López – Jiménez, Laura & Vallvé – Romeu, Alba & Serrano, Eduardo & Gutiérrez-Maldonado, José. (2019). The influence of gender and body dissatisfaction on body-related attentional bias: a study of eye-tracking and virtual reality. International Journal of Eating Disorders. 52. 10.1002 / menjar.23136.

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